PURPOSE: To automatically switch over inter-slave set communication via a master station or inter-slave set direct communication by providing a means selecting the inter-slave communication via the master set or inter-slave set direct communication.

CONSTITUTION: In the communication system comprising a master set 10 and plural slave sets (11,12) and in which the plural slave sets (11,12) obtain access to the master set with a common channel in time division, communication between slave sets is made while switching over mutually a route 14 for inter- slave set communication via the master station and a route 15 for inter-slave set direct communication while a slave set compares a transmission signal level of an opposite side slave set with a transmission signal level of the master set. Thus, since the speech route by the inter-slave set communication via the master set 10 and the speech route by the inter-slave set communication is automatically switch over mutually in the inter-slave set communication system, the user does not require manual operation for the inter-slave set direct communication.